I will investigate factors that may be important in determining neuronal lineages in the frog embryo. Quantitative fate maps derived from intracellular injections of the lineage marker, horseradish peroxidase, have recently been constructed for the 16- and 32-cell stage blastulae. The proposed experiments will perturb the normal blastomere arrangement in a variety of ways in order to determine, by comparison to the normal quantitative fate map, whether the phenotype and number of neurons are determine by gap junctional communication between cells, calcium- dependent interactions, direct cell-cell contact, and/or cytoplasmic moieties. The results of these experiments will identify the cellular interactions that are necessary at cleavage stages for the expression of neuronal lineages. They will lead to the investigation of these interactions at the cellular (cell surface and/or secreted products) and molecular (stored on mRNAs and proteins) levels. These studies are designed to allow analysis of the molecular interactions that affect the developmental decisions to form the vertebrate nervous system. The candidate, whose background is in developmental neurobiology and lineage analysis, intends to receive training in cellular/biochemical techniques in order to pursue studies of the molecular interactions that occur at the cell surface to affect neuronal lineages. She also intends to receive training in molecular techniques, in order to isolate, identify and clone cytoplasmic mRNAs or proteins that are involved in neuronal lineage determination of certain blastomeres. The RCDA will relieve her of teaching efforts, giving her time to receive this training and to establish research collaborations with cell surface/receptor molecular biologists. This training is necessary for her to achieve her long-term career goal of investigating the molecular interactions between early embryonic cells that affect the first steps in neuronal lineage determination in the vertebrate CNS. The University of Virginia provides a rich research environment in membrane/receptor studies, molecular biology and molecular interactions in developmental determination. By having her teaching duties drastically reduced, by providing formal training in two relevant laboratories, and by providing institutional support for several core research facilities, Dr. Moody will be able to accomplish her career goals to be an independent investigator in the field of molecular neurodevelopmental biology.